Maturation of soybean somatic embryos and the transition to plantlet growth.

The maturation of soybean (Glycine max L. Merr.) somatic embryos was characterized. Maturation was assayed by evaluating the ability of somatic embryos to make the transition to a plantlet through a germination-like process. Somatic embryos were organized from cotyledons of immature soybean embryos. Maturation of somatic embryos occurred on a Murashige-Skoog basal medium supplemented with activated charcoal and 0.28 molar sucrose. After 8 weeks on this medium, somatic embryos exhibited vigorous, high frequency development to plantlets. The "germination" frequency (conversion) of somatic embryos, and plantlet recovery frequency varied concurrently with maturation period. Conversion and plant recovery required no exogenous growth regulators. Desiccation of immature somatic embryos under controlled humidity regimes resulted in increased frequency of conversion of immature somatic embryos. Morphological abnormalities appeared in the somatic embryos, but few were detrimental to conversion velocity. There was little effect of genotype on conversion velocity or frequency.